For the first time in Vietnam, morphological and molecular studies of a species belonging to Bacillariophyceae collected in Northern coast of Vietnam are presented. Observations with microscope showed that this species belong to genus: Pseudo-nitzschia and seem like P. pungens. Sequence data from the partial 18S small subunit ribosomal RNA gene (18S rDNA) and the internal transcribed spacer 1 - 5.8S - internal transcribed 2 have been used to determine clearly and generate a phylogenetic framework of the obtained sequences to previously reported sequences in GenBank. These results allowed us to highlight described species of Bacillariophyceae in Northern coast of Vietnam. Furthermore, accumulation of molecular study would be helpful for the identification of scientific name of harmful algal species and further taxonomic studies in Vietnam.